For fuel economy reasons, automotive vehicles are being equipped with humidity/fog sensors. The type of sensor typically being used has a humidity sensor and often two temperature sensors and will be referred to herein as relative humidity/temperature sensor. One temperature sensor is located adjacent the relative humidity sensor and senses temperature of the air at the relative humidity sensor, that is, the air of which the relative humidity is being sensed by relative humidity sensor. The other temperature sensor is located so that it abuts a surface on which the relative humidity/temperature sensor is mounted, such as glass of a windshield. The relative humidity/temperature sensor is located in the vehicle so that it measures relative humidity and the temperature of the air the relative humidity of which is being sensed by the relative humidity sensor. As such, this type of sensor can also be used to sense the dew point of the air in the cabin. For example, the dew point of the air in the cabin can be calculated using the relative humidity and temperature readings obtained from the sensor. In normal operation, when sensing humidity, the temperature sensor senses a temperature that is between an average temperature of the cabin air and a temperature of exterior air outside the vehicle. When the relative humidity/temperature sensor is attached to an interior surface of a windshield of the vehicle, the glass temperature sensor senses the temperature of the glass of the windshield.
In heating, ventilation, air-conditioning (HVAC) systems in vehicles having automatic temperature control, the temperature of the air in the vehicle cabin, referred to herein as cabin air temperature, and the outside air temperature are typically used as inputs to a controller of the HVAC system that is configured to control it. In some cases, a sun load on the vehicle cabin is also used as an input to the controller. Heretofore, a sun load sensor has been used to provide this input. The controller is configured to use the input from the sun load to take into account a sun load on occupants of the vehicle and adjust the HVAC automatic temperature control accordingly. For example, the controller is configured to increase cooling when the sun load on vehicle occupants is higher and decrease cooling, or even change to heating, when sun loads are lower. To increase cooling due to a higher sun load, the controller is configured to increase the speed of a blower of the HVAC system, change temperature doors in the HVAC system to deliver colder air, and/or change the HVAC mode from a heating mode to a cooling mode. The amount that the controller is configured to increase cooling is based on the level of the sun load on the vehicle occupants—the higher the sun load the greater the increase in cooling.